TWI896318B - Process for preparing organotin compounds - Google Patents

Abstract

Provided is an efficient and effective process for preparing certain organotin compounds having alkyl and alkylamino substituents. The process provides the organotin compounds in a highly pure crystalline form which are particularly useful as precursors in the deposition of high-purity tin oxide films in, for example, extreme ultraviolet light (EUV) lithography techniques used in the manufacture of certain microelectronic devices.

Description

Method for preparing organotin compound

The present invention relates to the field of organotin chemistry. Specifically, it relates to an efficient and effective method for preparing certain organotin compounds, such as isopropyltris(dimethylamino)tin.

Certain organotin compounds have been shown to be suitable for depositing high-purity tin(II) oxide in applications such as extreme ultraviolet (EUV) lithography, which is used to make certain microelectronic devices. Of particular interest are organotin compounds with combinations of alkylamino and alkyl groups, which can be difficult to obtain in high purity.

Therefore, there is a need to provide an improved method for producing such organotin compounds in a highly pure form for use in depositing highly pure tin oxide thin films.

Provided herein is a method for preparing certain organotin compounds having alkyl and alkylamino substituents, such as compounds of formula (I): _R1 -Sn-( _NR2 ) ₃ , wherein R, which may be the same or different, is a _C1 - _C4 alkyl group and _R1 is a substituted or unsubstituted saturated or unsaturated linear, branched, or cyclic _C1 - _C5 group. A specific example of a compound of formula (I) is isopropyltris(dimethylamino)tin (CAS No. 1913978-89-8). The method comprises contacting a compound of formula (A), described in more detail herein, with a compound of formula _R1 -X, wherein X is bromine, iodine, or chlorine. The method also produces a compound of formula (II), and the present invention also relates to such a compound. Advantageously, the method provides the organotin precursor compound of formula (I) in a highly pure form (e.g., greater than 98% purity). Due to their high purity, the organotin compounds described herein are particularly suitable for depositing high-purity tin oxide (SnOx) thin films, such as in extreme ultraviolet (EUV) lithography techniques used in microelectronic device fabrication.

The present invention relates to a method for preparing organotin compounds having alkyl and alkylamino substituents.

In a first embodiment, the present invention provides a method for preparing a monoalkyl tin(dialkylamino) tin compound of formula (I): In this formula, each R may be the same or different and is a C ₁ -C ₄ alkyl group, and R ₁ is a substituted or unsubstituted saturated or unsaturated linear, branched or cyclic C ₁ -C ₅ group. The method comprises: , contacting a compound having the formula R ₁ -X, wherein X is bromine, iodine, or chloride. In one embodiment of this method, each R can be independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, and dibutyl. In a specific embodiment, each R is methyl. Additionally, R ₁ can be selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, dibutyl, n-pentyl, isopentyl, or neopentyl. Additionally, R ₁ can be a cyclic C ₁ -C ₅ group, such as a cyclopropyl group. Additionally, R ₁ can be an unsaturated C ₁ -C ₅ group, such as a vinyl group or an ethynyl group. Any of these R ₁ groups can be further substituted, such as with one or more halogen or ether groups. For example, _R1 can be a fluorinated alkyl group having _the formula -( _CH2 ) _n ( _CHaFb ) _m , where m = 1 to 5 and m + n = 1 to 5 and b = 1 to 3 and a + b = 3, including monofluorinated _C1 - _C5 alkyl groups (such as _-CH2F or _-CH2CH2F groups) and perfluorinated _C1 - _C5 groups (such as _-CF3 or _{CF2CF3 groups} ). Alternatively, _R1 can be an alkyl ether group, where the alkyl portion is _{a C1} - _C5 alkyl group. In a particular embodiment, _R1 is an unsubstituted C1- _{C5 alkyl} group, such as a _C1 - _C3 alkyl group. For example, each R can be methyl and _R1 can be isopropyl.

As indicated above, the starting material used in this method is a compound of formula (A): This compound can be prepared by known methods, such as by reacting tin(II) chloride (SnCl ₂ ) with a compound of formula MN(R) ₂ , wherein M is a metal selected from sodium, lithium, and potassium. Therefore, one embodiment of the present invention is a method for preparing a compound of formula (I), further comprising the prior step of preparing a starting material of formula (A) by reacting tin(II) chloride with a compound of formula MN(R) ₂ , wherein M is a metal cation, such as an Al cation, an Mg cation, or a Ca cation, or a Group 1 or Group 2 cation, such as a sodium ion, a lithium ion, or a potassium ion. As a specific example, M can be a lithium ion and R can be a methyl group. In such cases, the lithium chloride thus formed can be removed, for example, by filtration (if necessary), and the resulting compound of formula (A) can then be contacted with a compound of formula R ₁ -X. In other cases, the resulting starting material compound of formula (A) can be used as a slurry without filtration and reacted with the precipitated compound of formula M-Cl (e.g., lithium chloride) in the same reaction vessel. Thus, the present method provides a one-pot synthesis of compounds of formula (I).

The reaction provides a mixture of a compound of formula (I) as shown above and a by-product of formula (II): , wherein each R is the same or different and is a C ₁ -C ₄ alkyl group, and each X is selected from iodine, bromine, and chlorine. Therefore, the present invention further provides a byproduct compound of formula (II). For example, in one embodiment of this byproduct, each R is the same or different and is a C ₁ -C ₄ alkyl group, and each X is selected from iodine, bromine, and chlorine, with the proviso that when X is chlorine, R is not methyl. In another embodiment, each R is the same or different and is a C ₁ -C ₄ alkyl group, and each X is iodine or bromine. The crystal structure of the compound of formula (II), wherein each R is methyl and each X is iodine, is depicted in Figure 1. The byproduct of formula (II) is also expected to be useful as a precursor compound for depositing tin oxide thin films (such as tin(II) oxide or tin(IV) oxide thin films) and as an intermediate in the synthesis of other useful organotin precursor compounds.

The method of the present invention can be carried out neat (i.e., without any added solvent) or in a solvent that is inherently unreactive with the starting materials or products. Examples of suitable solvents include nonpolar aprotic solvents, including liquid hydrocarbons such as hexane, benzene, or toluene; polar aprotic solvents such as tetrahydrofuran or dimethoxyethane; and mixtures of nonpolar aprotic solvents and polar aprotic solvents. When carried out neat without any added solvent, an excess of the compound of formula R ₁ -X can be used, particularly when the compound is a liquid. Alternatively, the method can be carried out via an exchange reaction using a halogen exchange reagent in combination with the compound of formula R ₁ -X.

The method is carried out at a temperature suitable for the reaction of the disclosed reactants. For example, the reaction temperature can range from approximately room temperature (e.g., about 20° C.) to about 80° C. In a preferred embodiment, the method is carried out at a temperature from room temperature (23° C.) to about 65° C., such as from about 50° C. to about 70° C. or about 60° C.

As noted above, in the synthesis of the starting material of formula (A), the lithium halide by-product (e.g., LiCl) can be removed by filtration. The resulting starting material can be used as is in the same reaction vessel for further reaction with a compound of formula R ₁ -X to form a compound of formula (I), which can be further purified, for example, by distillation, to provide a product preferably having a lower content of impurities.

The present invention may be further illustrated by the examples included herein, but it will be understood that these examples are included for illustration purposes only and are not intended to limit the scope of the present invention unless specifically indicated otherwise. Example 1

Isopropyltris(dimethylamino)tin was prepared using the reaction sequence described above and shown below:

Therefore, a 3-neck, 500 mL round-bottom flask equipped with a magnetic stir bar was charged with 12.2 g of lithium dimethylamino (239 mmol) and 250 mL of hexane. To this off-white slurry was added 21.6 g of SnCl ₂ (113 mmol) and the resulting mixture was stirred at 60°C for 72 hours. The resulting off-green slurry was cooled to 23°C to obtain a mixture comprising the compound of formula (A).

Without further purification, the mixture was treated with 11.5 g of 2-iodopropane (68.2 mmol). The reaction mixture was then heated to 60°C for 18 hours. After the reaction mixture was cooled to 23°C, it was filtered through a coarse-pore sintered filter into a 500 mL flask, and the filter cake was washed with a 500 mL aliquot of anhydrous hexane to obtain a clear, pale yellow solution. The solvent and other volatiles were then removed from the filtrate under reduced pressure to produce a mixture of the product of Formula (I) and the by-product of Formula (II).

When volatile removal was complete, the remaining oil was filtered through a 0.2 μm syringe filter to yield 10.6 g of an orange oil. The orange oil was placed in a -30°C freezer overnight to allow [ISn(NMe ₂ )] ₂ to precipitate as a yellow solid. This yellow solid was removed by filtration through a 0.2 μm syringe filter. The remaining orange oil was then distilled using short-path distillation at 610-645 mTorr with a top temperature of 34-37°C to yield isopropyltris(dimethylamino)tin (6.09 g, 36.5%) as a clear, pale yellowish-green oily distillate. ^1H -NMR (400 MHz, benzene-d6): δ 2.83 ( ^1H - ^119/117Sn ) = 20.8 Hz, 18H), 1.68-1.57 (m, 1H), 1.27 (d, J1h-13C = 7.3 Hz, 6H). ^119Sn NMR: 64.30. Figures 2A and 2B show the ^119Sn -NMR and ^1H -NMR spectra, respectively, indicating that the product is of high purity.

The byproduct [ISn( _NMe2 )] ₂ was found to be a crystalline solid and therefore also possessed high purity, such as greater than 95% purity, including greater than 98%, 99%, or 99.5%. The crystal structure is shown in Figure 1, and crystallinity data are provided in Tables 1 and 2. Due to their high purity, these organotin compounds are expected to be suitable for depositing high-purity tin oxide thin films, such as in extreme ultraviolet (EUV) lithography techniques used in microelectronic device fabrication. Table 1 - Crystallographic Data and Structural Refinement of [ISn( _NMe2 )] ₂ . Experiential C4 H12 I2 N2 Sn2 Molecular formula C4 H12 I2 N2 Sn2 Formula 579.34 temperature 100.15 K Wavelength 0.71073 Å Crystal system orthorhombic Space Group Pbcn Unit cell size a = 22.0958(5) Å α= 90°. b = 10.2623(3) Å β= 90°. c = 10.9856(3) Å γ = 90°. Volume 2491.03(11) Å ³ Z 8 Density (calculated value) 3.090 Mg/m ³ Absorption coefficient 8.919 mm ^-1 F(000) 2048 Crystal size 0.2 × 0.18 × 0.18 mm ³ Lens color, habitual Pale yellow crystal blocks Theta range used for data collection 1.843 to 27.102°. Index range -28＜=h＜=28, -13＜=k＜=12, -14＜=l＜=14 Collected reflections 25802 Independent reflex 2748 [R(int) = 0.0740] θ = 25.242° of integrity 100.0% Absorption correction Semi-empirical absorption correction based on equivalent values Maximum and minimum transmittance 0.2616 and 0.1599 Refinement method Least squares method for the full matrix of ^F2 Data/Limits/Parameters 2748 / 0 / 96 Suitability for ^F2 1.259 Final R index [I＞2σ(I)] R1 = 0.0291, wR2 = 0.0713 R index (all data) R1 = 0.0300, wR2 = 0.0720 Extinction coefficient 0.00069(5) The maximum peak and valley on the difference graph 1.367 and -0.890 e.Å ^-3 Table 2 - Bond lengths [Å] and bond angles [°] of [ISn(NMe ₂ )] ₂ Key length: I(1)-Sn(1) 2.8492(5) I(2)-Sn(2) 2.8448(5) Sn(1)-N(1) 2.252(4) Sn(1)-N(2) 2.267(4) Sn(2)-N(1) 2.245(4) Sn(2)-N(2) 2.243(4) N(1)-C(1) 1.477(6) N(1)-C(2) 1.484(6) N(2)-C(3) 1.480(7) N(2)-C(4) 1.482(6) C(1)-H(1A) 0.9800 C(1)-H(1B) 0.9800 C(1)-H(1C) 0.9800 C(2)-H(2A) 0.9800 C(2)-H(2B) 0.9800 C(2)-H(2C) 0.9800 C(3)-H(3A) 0.9800 C(3)-H(3B) 0.9800 C(3)-H(3C) 0.9800 C(4)-H(4A) 0.9800 C(4)-H(4B) 0.9800 C(4)-H(4C) 0.9800 Key angle: N(1)-Sn(1)-I(1) 98.21(10) N(1)-Sn(1)-N(2) 78.97(14) N(2)-Sn(1)-I(1) 95.40(11) N(1)-Sn(2)-I(2) 93.25(10) N(2)-Sn(2)-I(2) 92.67(11) N(2)-Sn(2)-N(1) 79.62(14) Sn(2)-N(1)-Sn(1) 97.25(14) C(1)-N(1)-Sn(1) 118.1(3) C(1)-N(1)-Sn(2) 108.3(3) C(1)-N(1)-C(2) 108.3(4) C(2)-N(1)-Sn(1) 110.2(3) C(2)-N(1)-Sn(2) 114.5(3) Sn(2)-N(2)-Sn(1) 96.88(15) C(3)-N(2)-Sn(1) 119.8(3) C(3)-N(2)-Sn(2) 105.7(3) C(3)-N(2)-C(4) 108.0(4) C(4)-N(2)-Sn(1) 110.1(3) C(4)-N(2)-Sn(2) 116.5(3) N(1)-C(1)-H(1A) 109.5 N(1)-C(1)-H(1B) 109.5 N(1)-C(1)-H(1C) 109.5 H(1A)-C(1)-H(1B) 109.5 H(1A)-C(1)-H(1C) 109.5 H(1B)-C(1)-H(1C) 109.5 N(1)-C(2)-H(2A) 109.5 N(1)-C(2)-H(2B) 109.5 N(1)-C(2)-H(2C) 109.5 H(2A)-C(2)-H(2B) 109.5 H(2A)-C(2)-H(2C) 109.5 H(2B)-C(2)-H(2C) 109.5 N(2)-C(3)-H(3A) 109.5 N(2)-C(3)-H(3B) 109.5 N(2)-C(3)-H(3C) 109.5 H(3A)-C(3)-H(3B) 109.5 H(3A)-C(3)-H(3C) 109.5 H(3B)-C(3)-H(3C) 109.5 N(2)-C(4)-H(4A) 109.5 N(2)-C(4)-H(4B) 109.5 N(2)-C(4)-H(4C) 109.5 H(4A)-C(4)-H(4B) 109.5 H(4A)-C(4)-H(4C) 109.5 H(4B)-C(4)-H(4C) 109.5 Example 2

F ₃ CSn(NMe ₂ ) ₃ was prepared using the reaction sequence described in Example 1. Specifically, [Sn(NMe ₂ ) ₂ ] ₂ (23.1 g, 55.6 mmol) was charged to a 250 mL round-bottom flask equipped with a magnetic stir bar and dissolved in hexane (125 mL). The flask was equipped with a cylinder of I-CF ₃ (25 g, 127.6 mmol) via 1/4 PTFE tubing and a 24/40 tube adapter. Slowly, in the dark, I-CF ₃ was bubbled into the hexane solution while stirring. After approximately 10 minutes, the reaction showed a yellow precipitate. After approximately 30 minutes, all the gas had been added, and the reaction showed a flocculent yellow precipitate. The cylinder was then removed and mass measurements were taken to confirm that all the required I-CF ₃ had been added. The reaction was covered with foil and stirred at room temperature in the dark over the weekend. Afterwards, the reaction developed a yellow/tan precipitate and was filtered through a disposable polyethylene fritted glass filter and washed with hexane (25 mL). The resulting pale yellow solution was dried under reduced pressure until approximately 5 mL remained. ¹ H-NMR, ¹⁹ F-NMR, and ¹¹⁹ Sn-NMR of a C ₆ D ₆ solution of the product showed that hexane (approximately 5 mol) remained. A tan solid (28.7 g) and 4 g (22.5%) of a slightly yellow liquid were isolated. ¹ H-NMR (C ₆ D ₆ , 400 MHz); s, 18H, 2.69 ppm; ¹¹⁹ Sn-NMR (C ₆ D ₆ , 150 MHz); q, -153.07 ppm; ¹⁹ F-NMR (C ₆ D ₆ , 376 MHz); -42.7 ppm. Example 3

F ₃ CCH ₂ Sn(NMe ₂ ) ₃ was prepared using a procedure similar to that described in Example 2. Specifically, [Sn(NMe ₂ ) ₂ ] ₂ (140 g, 336 mmol) was placed in a 1 L Schlenk flask equipped with a magnetic stir bar and diluted with approximately 400 mL of hexane to form a yellow mixture. I-CH ₂ -CF ₃ was placed in a 250 mL addition funnel and connected to the Schlenk flask. A slow addition rate (approximately 0.5-1 drops/second) was achieved, and the 1 L flask was covered with aluminum foil and stirred in the dark. After approximately 2.5 hours, the addition of I-CH ₂ CF ₃ was complete, and the resulting yellow mixture was stirred overnight at room temperature in the dark. After this time, the reaction produced a bright yellow solid precipitate and a red/orange solution. The precipitate was separated by filtration through a disposable polyethylene fritted glass filter into a 500 mL Schlenk flask equipped with a magnetic stir bar. The filter cake was washed with hexane (approximately 30 mL), and the resulting orange solution was dried under reduced pressure to yield a pale yellow solution with a yellow precipitate. The mixture was filtered through a 0.2 μm syringe filter into two amber 40 mL tared vials, yielding 87.91 g (78.5% crude yield) of the product as a pale yellow liquid. ^1H -NMR, ^19F -NMR, and ^119Sn -NMR results of a 1:1 product:C ₆ D ₆ solution: ^1H -NMR (C ₆ D ₆ , 400 MHz); s, 18H, 2.66 ppm; q, 2H, 1.52 ppm; ^119Sn -NMR (C ₆ D ₆ , 150 MHz); q, -62.47 ppm; ^19F -NMR (C ₆ D ₆ , 376 MHz); q, -51.93 ppm.

The invention has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Figure 1 is a depiction of the crystal structure of the compound of formula (II) produced as a by-product of the process as described herein, wherein each R is methyl and each X is iodine.

Figures 2A and 2B are the ¹¹⁹ Sn-NMR and ¹ H-NMR spectra, respectively, of a compound of formula (I) obtained in d6-benzene as a product of the process described herein, wherein each R is methyl and R ₁ is isopropyl.

Claims (9)

A compound of formula (I), , wherein each R may be the same or different and is a C ₁ -C ₄ alkyl group, and R ₁ is a branched chain C ₃ -C ₅ alkyl group, wherein the compound contains less than 5% to more than 0% , wherein each R may be the same or different and is a C ₁ -C ₄ alkyl group, and X is selected from iodine, bromine and chlorine. The compound of claim 1, wherein each R is independently methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, or dibutyl. The compound of claim 1, wherein each R is a methyl group. The compound of claim 1, wherein the compound is dissolved in a non-polar solvent. The compound of claim 1, wherein R ₁ is isopropyl. A compound of formula (I), , wherein each R may be the same or different and is a C ₁ -C ₄ alkyl group, and R ₁ is a cyclic C ₃ -C ₅ group, wherein the compound contains less than 5% to more than 0% , wherein each R may be the same or different and is a C ₁ -C ₄ alkyl group, and X is selected from iodine, bromine and chlorine. The compound of claim 6, wherein each R is independently methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, or di-butyl. The compound of claim 6, wherein each R is a methyl group. The compound of claim 6, wherein the compound is dissolved in a non-polar solvent.